Saturday, September 01, 2012

New FanGraphs Stats Complement WAR

There has been much criticism of the Wins Above Replacement (WAR) statistic at FanGraphs over the last couple of years. This metric (sometimes called fWAR to distinguish it from other WAR statistics) is designed to give a pitcher credit for everything he controls with little help from others - strikeouts, bases on balls, hit batsmen and home runs. These are said to be Fielding Independent Pitching (FIP) or Defense Independent Statistics (DIPS).

As an example, Tigers right hander Max Scherzer has allowed 54 walks and 22 home runs, has hit 3 batters and has 195 strikeouts in 154 2/3 innings this year. This translates into a FIP ERA of 3.57 which is the ERA a pitcher "should" have given those numbers. This is more than a half run lower than his actual ERA of 4.13.

A pitcher who allows 3.57 earned runs per nine innings over 154 2/3 innings theoretically adds about three (3.2 WAR) wins above what a "replacement" pitcher would contribute. On the other had, if Wins was based on runs allowed per nine innings (RA9), Scherzer would be a little more than two wins (2.4 RA9-Wins) above a replacement-level pitcher. That's a fairly substantial difference and such discrepancies happen often, which is one of the sources of skepticism regarding WAR.

There are two main reasons why WAR (based on FIP) can be different from RA9-Wins:

RA9-Wins gives pitchers full credit/blame for results of batted balls in
play despite the fact that they share that responsibility with
fielders. For example, a pitcher with a strong defense behind him will
tend to give up fewer hits (and thus fewer runs) than if he had a poor
defense behind him. fWAR, on the other hand gives a pitcher zero responsibility for what happens on balls in play.

RA9-Wins gives pitchers full responsibility for sequencing or timing of
events, that is, it assumes that they can control when they give up hits
and walks. For example, if a pitcher pitches extraordinarily well with
runners in scoring position in a given year, he will have a lower ERA
than if he had a typical year in those situations. Additionally, a
pitcher who tends to bunch base runners together in single innings will
have a higher ERA than if he had a typical year distributing base
runners more evenly. WAR gives a pitcher zero credit/discredit for sequencing.

In reality, neither RA9-Wins nor WAR is correct for every pitcher because the amount of control pitchers have over number of batted
balls that drop for hits and sequencing of events falls somewhere between 0 and 100. The problem is nobody knows exactly how much control a pitcher has over these things and the percentage probably varies from pitcher to pitcher. So, FanGraphs is sticking to its FIP-based WAR while acknowledging that it doesn't explain everything about a pitcher's performance.

RA9-Wins = Wins for a pitcher based on total runs scored while he is pitching
WAR = Wins for a pitcher based on SO, BB, HBP, HR
FDP-Wins = RA9-Wins minus WAR = Wins not accounted for by SO, BB, HBP, HR
BIP-Wins = Wins contributed by outcomes of balls in play
LOB-Wins = Wins contributed by sequencing of events or runners left on base.

The negative number for BIP-Wins tells us that Scherzer has not had good results on balls in play. This is also seen in his unusually high .347 Batting Average on Balls in Play (BABIP). This could be a result of poor fielding support (we know the Tigers don't offer much of that) or bad luck on balls in play. We don't want to assume that none of it his his fault though. While pitchers do share the responsibility of results of batted ball with fielders, some pitchers do get hit harder than others. These are questions that can't be fully answered until complete data on speed, distance and trajectory of batted balls become freely available.

Scherzer's positive number for LOB-Wins reveals that the runners he does allow have not been scoring at a high rate. How much of this is skill as opposed to good fortune is not known. We do know that his 76% LOB% is higher than his career mark of 73%, so perhaps he has been a bit lucky in that respect this year.

These new statistics certainly don't answer all the questions about pitching, but it's good to see runs allowed, WAR, results of balls in play and runners left on base all in the same unit (wins) and all on the same page. I'll be examining these numbers for other Tigers pitchers in future posts.